Haptic user interface for robotically controlled surgical instruments

ABSTRACT

A powered user interface for a robotic surgical system includes a handle on a linkage having a plurality of joints, a base, and actuators. The interface operates in accordance with a first mode of operation in which a plurality of its actuators are operated to constrain predetermined ones of the joints to permit motion of the handle in only 4DOF with respect to the base, and a second mode of operation in which the actuators permit motion of the handle in at least 6DOF with respect to the base.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of surgical systemsusing electromechanical drivers to effect movement of medicalinstruments within a body cavity. More particularly, the inventionrelates to a haptic user interface for such systems.

BACKGROUND

Surgical systems used for robotically-assisted surgery or roboticsurgery employ electromechanical drivers to drive movement of surgicaldevices or instruments within a body cavity, typically in response tosignals generated when a user moves a user input device. Examples ofsuch systems are those shown and described in U.S. Pat. No. 9,360,934,International Publications WO 2007/088206, WO 2008 049898, and WO 2016057989. In a typical system, movement of the surgical device is achievedby using a robotic manipulator arm to robotically reposition or reorientthe surgical device and/or by causing movement of some portion of thesurgical device (e.g. an instrument end effector) relative to anotherportion of the surgical device. Input to the system is generated basedon input from a surgeon positioned at a master console, typically usingprimary input devices such as input handles that the surgeon moves inthe way he or she might use manual surgical instrument handles whenoperating using manual instruments.

The number of degrees of freedom (DOFs) of motion for a roboticallycontrolled surgical device can vary between surgical systems and alsobetween the different devices used for a particular system. Arobotically controlled rigid-shafted instrument that moves similarly toa conventional laparoscopic instrument will have the 4 DOFs of pitch andyaw (each by pivoting the rigid instrument shaft relative to a fulcrumat the incision site), axial roll about the longitudinal axis of theinstrument, and translation along the longitudinal axis of theinstrument (along the axis of insertion/withdrawal of the instrumentrelative to the incision). Additional degrees are present for devices orinstruments having greater complexity. For example, an instrument thatincludes an elongate rigid shaft having a region that can be roboticallycontrolled to articulate or bend can have additional DOFs in the regionof the articulation or bend. As a more specific example, such aninstrument might be configured to move the instrument tip or endeffector in pitch and/or yaw relative to the instrument shaft (i.e. inaddition to the pitch and/or yaw that results from movement of the rigidinstrument shaft about a fulcrum at the incision site), giving theinstrument 6DOFs.

There are two typical types of user instrument handle motion used insurgery. In laparoscopic surgery, the instrument shafts pivot about afulcrum at the incision site. Thus when the surgeon moves the instrumenthandle upwardly, the tip of the instrument moves downwardly in the body.Surgical robotic systems designed for use by laparoscopic surgeonssimulation this motion, providing user interfaces having handles thatmove and give input in a manner familiar to the surgeons. UI handlesthat move in accordance with laparoscopic motion are operated in a 4DOFmode of operation in which the handle motion is often limited to yaw,pitch, roll and insertion.

Another type of instrument handle motion used in surgery is referred toas “true cartesian motion,” which differs from laparoscopic motion inthat there is no inversion of the motion.

Some user interfaces for robotic laparoscopy are designed to receiveuser input to control the 4 DOFs of laparoscopic instruments, plus jawactuation, but lack the capability to actuate additional degrees offreedom should articulating or wristed instruments be used on therobotic system. This application describes a user interface havingsufficient degrees of freedom to control operation of 6DOF instrumentsand/or to operate in accordance with true cartesian motion, but thatalso can be placed in a mode of operation in which the input handlemoves with respect to a virtual fulcrum establish at the UI, thusallowing control of a 4DOF instrument using motions akin to those thatwould be used to manually move a laparoscopic instrument.

As described in application US 2013/0012930, the ability to understandthe forces that are being applied to the patient by the roboticallycontrolled surgical devices during minimally invasive surgery is highlyadvantageous to the surgeon. Communication of information representingsuch forces to the surgeon via the surgeon interface is referred to as“haptic feedback.” In some systems, haptic feedback is communicated tothe surgeon in the form of forces applied by motors to the surgeoninterface, so that as the surgeon moves the handles of the surgeoninterface, s/he feels resistance against movement representing thedirection and magnitude of forces experienced by the roboticallycontrolled surgical device. Forces represented can include both theforces at the tips of the robotically controlled devices and/or theforces being applied by the shaft of the robotically controlled deviceto the trocar at the entrance point to the body, giving the surgeoncomplete understanding of the forces applied to the device so s/he canbetter control the device during surgery.

The present application describes a powered 6DOF (or higher) haptic userinterface (UI) that may be used by a surgeon to input surgeon commandsfor control of a 6DOF surgical device, and to receive force feedback(including orientation haptics) representing forces experienced by thatsurgical device. Many prior art haptic user interfaces do not provideorientation haptics. Those that do typically use a heavy gimbalmechanism with motors near where the user manipulates the user interfacehandle, cantilevered far from the base of the UI mechanism. Thecantilevered mass of the gimbal/motor assembly requires that the othermotors in the mechanism consume more power to provide haptic feedback(due to inertial loading) and perform gravity compensation (due to largemoment loads). This also means that these other motors have to be largerin order to avoid overheating, or have to be mated to a gear reduction,which introduces backlash and makes the mechanism more difficult for theuser to manipulate (due to mechanical disadvantage). Additionally, theincreased inertia near the location where the user manipulates the userinterface handle means that the user will have to overcome greaterinertial forces in order to move the handle. Additionally, in otherdevices, the motors that are located at a distance from the base of theUI mechanism require electrical cables (power, sensors, etc.) to berouted some distance along the mechanism.

The mechanism described herein is capable of providing orientationhaptic feedback to user while eliminating use of a powered gimbalmechanism, reducing cantilevered weight, simplifying electrical andmechanical cabling, and using smaller motors and reduced powerconsumption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are perspective views of a powered user interface;

FIG. 3 schematically shows the powered and measured joints of thepowered user interface shown in FIG. 1;

FIG. 4 is a partially exploded view of a gimbal interface of theinterface of FIG. 1;

FIG. 5 is a kinematic diagram showing the degrees of freedom of the userinterface of FIG. 1, with the right hand side of the drawingrepresenting the handle, shaft and gimbals.

FIG. 6 illustrates cable routing of the interface of FIG. 1;

FIG. 7 shows a perspective view of a second embodiment of a powered userinterface;

FIG. 8 illustrates the motors, gears, and shafts for a bevel gearimplementation used to drive joints of the first or second embodiment.This drawing only shows the gears and shafts and does not show thelinkage arms.

FIG. 9 illustrates use of belts and/or cables to transfer motion fromthe motors to the center of axes of motion in the first or secondembodiment.

FIG. 10 depicts RCM constraint algorithms that may be used in methodsfor operating the 6DOF (or higher) user interface in a 4DOF mode.

DETAILED DESCRIPTION

This application describes a user interface that is designed to bemanipulated by a user to generate signals that are used to commandmotion of a robotically controlled device, and to provide hapticfeedback to the user in six degrees of freedom. Note that thisapplication will describe the user interface in the context of a roboticmanipulator having a surgical instrument as the robotically controlleddevice, but it should be understood that the interface may be used forother types of robotically controlled devices.

The interface device is capable of providing a user experience similarto that of controlling a laparoscopic instrument and does so byvirtually creating a haptic rotational center-of-motion (RCM) constraintat the UI using the haptic motors. In use the interface is preferablypositioned at a surgeon console in which the surgeon sits or stands andmanipulates the UI while observing an image of the surgical operatingspace within the body on an image display including, without limitation,a console-mounted or wearable image display.

The user interface is a six degree-of-freedom (DOF) mechanism containingelectric motors that can provide haptic feedback to the user. The usermanipulates the user interface by grasping a handle attached to the userinterface. The position of any point rigidly attached to the handle, aswell as the orientation of the handle, is determined based on themeasured position of six joints. The haptic forces provided to the userare delivered by six electric motors. The position of the six joints isdetermined using sensors that are attached to the motors. The positionand orientation of the handle is reconstructed (in software) from themeasurements of all of the sensors. For example, the position along thex-ordinate depends on the positions of all six sensors, not just one.

The handle of the instrument is used to actuate the jaw (or otherfeature) of a robotically controlled surgical device/instrument,although this motion is not counted as one of the six DOFs mentionedabove. However, it is independently actuated/measured by a motor/sensorthat may be located in the handle.

The user interface is incorporated into a user workstation, which mayinclude one or more such user interfaces, as well as a video displayallowing the user to view images taken from a laparoscope or other typeof camera disposed within the patient. In one implementation of the userinterface 100, shown in FIGS. 1 and 2, a linkage system 102 is supportedat the user workstation (not shown) by a base 10. Base 10 includes abase motor 12 (FIG. 2). A linkage assembly 14 is rotationally coupled tothe base 10 such that operation of base motor 12 rotates the linkage 14relative to the base 10. Two linkage arms 16 a, 16 b are mounted to thelinkage 14. Each of the arms 16 a, 16 b comprises two active degrees offreedom and at least two passive degrees of freedom. In this embodiment,those active degrees of freedom are driven by four additional motors Mmounted on the linkage 14 (labeled in FIG. 1). Additional active degreesof freedom allow roll about the handle axis and closure of the handleswith respect to one another. The motors for these features are notshown. An additional passive degree of freedom allows the sliding of thehandle shaft with respect to the end of one arm, although a secondembodiment described below does not include this DOF.

The kinematics of the UI will be best understood with reference to FIG.3, which is similar to FIG. 1, but which does not show the base 10 andwhich shows linkage 14 only schematically. The location of the sixjoints J1-J6 of the user interface are shown, all of which are capableof being independently actuated and measured by their respective motorsM and sensors (not shown). In this implementation, all six joints arerevolute joints, and their axes of rotation are indicated by thedirection of the dashed lines in the figure. Here the two two-barlinkages (each being one of the arms 16 a, 16 b) are shown schematicallymounted upon linkage 14, which is a rotating platform rotatable relativeto the base 10 (not shown). In this embodiment the arms 16 a, 16 b areparallel to one another, while in the second embodiment they are notfixed in a parallel relationship to one another. The rotating platform14 is actuated/measured by J1. J2 and J4 actuate/measure the proximal(nearest to the handle) two-bar linkage 16 a, while J3 and K5actuate/measure the distal (furthest from the handle) two-bar linkage 16b. In this embodiment, the axes of J2-J5 are always parallel to oneanother. The four motors M (FIG. 1) that actuate/measure J2, J3, J4 andJ5 are all mounted upon the platform 14 controlled by joint 1. J4 isactuated via cables or other means that are routed along the length ofthe link between J2 and J4. In one implementation, described in moredetail below, these cables are routed around a pulley located at J2 thatis concentric with the joint 2 axis. Therefore, motion of J2 affects theactuation/sensing of J3. This is compensated for in software. J3 and J5are identical to J2 and J4 in their construction and compensation.

A handle 24 with a shaft 26 is coupled to the two-bar linkages. The endof each two-bar linkage 16 a, 16 b includes a passive gimbal 18 a, 18 bthat allows the shaft 26 of the handle to yaw and pitch relative to thetwo-bar linkages 16 a, 16 b. See FIG. 4. In this embodiment, each gimbal18 a, 18 b includes an inner ring 20 a, 20 b and an outer ring 22 a, 22b (see reference numbers in FIG. 4). The shaft 26 of the handle 24 isfixed to the inner-most ring 20 a of the proximal gimbal 18 a. In thefirst embodiment, the shaft of the handle is able to slide freelythrough the inner-most ring 20 b of the distal gimbal 18 b. FIG. 4 is anexploded view showing the inner ring 20 a and outer ring 22 a of gimbal18 a along with a portion of shaft 26.

Referring again to FIG. 3, joint 6 can be measured/actuated in twodifferent ways. Either a small motor/sensor assembly can be mounted tothe shaft of the handle and used to actuate/measure joint 6, or joint 6can be actuated/measured via cables routed along the links of theproximal two-bar linkage 16 a. In the latter case, compensation for themotion of joints 2 and 4 is performed using software in order toaccurately measure the motion about J 6. FIG. 5 is a kinematic diagramshowing the degrees of freedom from the embodiment shown herein, withthe right hand side of the drawing representing the handle 24, shaft 26and gimbals 18 a, 18 b shown in the other drawings.

During use of the user interface, actuation of any combination of themotors (which, in use, results from the sensing of forces resulting frominteractions between the surgical device under robotic control andsurrounding structures) causes the user moving the handle 24 to feelresistance against movement in the DOFs.

Implementations that sense rotation about the roll axis (J6) for thepurpose of receiving input used to control the robotic surgicalinstrument, but that do not provide haptic constraint or feedback forthe roll axis as shown are also within the scope of the invention.Additional input devices or axes (passive, sensed, or sensed andactuated) may be added beyond those described above to provideadditional control capability, redundant control capability, orincreased range of motion and are within the scope of the invention. Oneexample of this may be a prismatic joint along the shaft 26 thatprovides additional range of motion for insertion.

For each actuated degree of freedom, various mechanisms may be used totransmit motion from the motors to the center of the actuated degree offreedom. In one implementation, cables are used to transmit motion fromthe motors to the center of the actuated degrees of freedom. Differencesin pulley size may be used to create a mechanical advantage. Cables,which may be metal, plastic, or a combination thereof, are wrappedaround a set of pulleys or capstans and tensioned to bidirectionallytranslate motion. Cables provide the advantage of light weight andminimal backlash, both of which are important for a haptic interface.

FIG. 6 is a cross-section view of the user interface shown in FIGS. 1-5,and further illustrates cable driving paths to the centers of the drivendegrees of freedom for joints J1-5. Note that the common shaft(s)communicate from the outer pulleys, through the proximal axes to theinner pulleys that drive the cables to actuate the distal axes of eacharm 16 a, 16 b. In other implementations, an additional cable or set ofcables running through the linkage(s) may be used to actuate therotational (roll) axis of the handle and/or the closure of the handle.

In alternative embodiments, gears are used to convey the motion from themotors to the axes. In some implementations, a combination of spur andbevel gears are used, but other gears, such as, but not limited to, spurgears, bevel gears, and helical gears. Features and components may beadded to reduce backlash.

FIG. 8 illustrates the motors, gears, and shafts for a bevel gearimplementation used to drive joints J2 through J5. Note that thisdrawing does not show the linkage arms 16 a, 16 b, only the gears andshafts. The dotted lines represent the position of two links of one ofthe linkage arms.

Referring to FIG. 9, in an alternative embodiment belts and/or cablesare used to transfer motion from the motors to the center of axes ofmotion. In some implementations, the difference in pulley size is usedto create a mechanical advantage. Timing belts may be used to reduceslipping, increasing positioning resolution and potential output torque.In the FIG. 9 embodiment, the paths of the belts are similar to those inthe cable implementation shown in FIG. 6, but alternative belt routesmay be used.

A second embodiment is shown in FIG. 7. The second embodiment differsfrom the first in that the handle shaft is not able to slide through thedistal gimbal. Instead, the handle shaft is constrained at the distalgimbal. An additional DOF is instead added at the shoulder joint of thedistal arm 16 b. This additional DOF is in the form of a slight pivot ina horizontal plane, which allows that shoulder joint to thus both rotatein a horizontal plane and moving up/down at J3 (this latter DOF alsobeing present in the first embodiment). This allows a shorter handleshaft to be used and it eliminates a sliding constraint in favor of arotating constraint.

Although two examples of 6DOF embodiments are shown, various otherembodiments within the scope of this disclosure can employ alternativeconfigurations for DOFs. For example:

-   -   In an alternative embodiment, a first, two-link, arm may be used        to mechanically (rigidly or haptically) define a remote center        of motion (RCM) through which a shaft slides, and a second arm        having at least three degrees of freedom may be used to define        the position of the end of the instrument shaft. With the        addition of a roll axis control similar to that defined above,        this combination of degrees of freedom may also be used to        define the motion in six-degrees of freedom. Having a visibly        fixed remote center of motion may provide additional familiarity        to a laparoscopic surgeon familiar with inserting an instrument        shaft through a trocar.    -   In another implementation, a pair of two-link arms on        separately-actuated rotational bases may be used to define        six-degree of freedom motion.

It should also be noted that alternative linkages to those shown anddescribed in this application may be instead be used as described hereto input and define motion in six degrees of freedom.

Control of 4DOF System Using a Greater than 4DOF UI

Another advantage of the disclosed system is that it is one that allowsa single user interface design to be used to control a robot indifferent ways, e.g. laparoscopic or true Cartesian motion. As discussedin the Background section, some robotic surgical systems controllaparoscopic surgical devices moveable in 4DOF, while other roboticsurgical systems control surgical devices moveable in more than 4DOF,such as 6DOF. The disclosed haptic interface is one type of powered userinterface that can be used to control either type of system, although itshould be understood that the method may be practiced using variousother UI designs having more than 4DOFs.

In accordance with this method, a UI having more than 4 DOFs can beoperated to deliver input used to control a 4DOF surgical device withoutrequiring the user to physically constrain his/her movement of thehandle to mimic laparoscopic instrument motion. Instead, the actuatorsused for haptic feedback are used to constrain the user interface suchthat the handle manipulated by the user moves only in the relevant4DOFs.

The four degrees of freedom necessary to control a 4DOF laparoscopicdevice are yaw and pitch (each with respect to a fixed fulcrum), rolland insertion. The UI described herein may be operated in a 4DOF mode ofoperation in which the handle motion relative to the base is limited toyaw, pitch, roll and insertion. Note that jaw open-close operation isnot considered a degree of freedom, so it should be understood that,when motion is limited to these four DOFs, jaw open-close can bepermitted. When the UI is operated in the 4DOF mode of operation, avirtual fulcrum or rotational center of motion (RCM) is created in theUI workspace. Note that the virtual RCM can be located at any point inthe workspace. It may be created at a point that is arbitrarily selectedby the system, or user-selected in response to a prompt, or pre-set at adefault setting (and optionally changeable by the user), or determinedor set in some other way.

Referring to FIG. 10, operation in the 4DOF mode of operation causes theactuators of the UI to orient the control Y-axis (line 1 shown in FIG.10) which points in the direction of the handle of the UI) to passthrough the RCM point, so that the handle of the instrument is caused bythe actuators to always point towards the RCM constraint. Thus once thevirtual fulcrum is set (or it may be pre-set at a default point) thehaptic actuators then generate corrective moments that will manipulatethe orientation of the UI handle such that its insertion axis passesthrough the virtual fulcrum point. The user moving the handle thusexperiences laparoscopic-style motion constrained relative to thevirtual fulcrum. Thus in this mode, the handle motion relative to thebase is limited by the actuators to pitch and yaw of the shaft of thehandle relative to the virtual fulcrum, axial roll about thelongitudinal axis of the handle shaft (“roll”), and translation alongthe handle shaft (“insertion”).

Using a first embodiment, the corrective moment is computed based on theerror between the actual orientation and the desired orientation (onewhose insertion axis intersects the virtual fulcrum). Referring to FIG.10, the corrective moment is proportional to the orientation error, andalso contains some viscous damping to prevent instability. In FIG. 10,the virtual fulcrum is labeled “RCM” (rotational center of motion) andthe UI handle is attached to control point P (a point located on theuser interface, such as on the handle, the position of which is knownbased on the kinematics of the user interface mechanism). The methodcauses the y-axis (line 1) at point P, which is the insertion axis andruns in the direction of the handle, to pass through the virtual RCM.

To do this, an algorithm is employed to determine the difference indirection between the control y-axis (line 1) and the vector from thecontrol point P to the RCM (line 2 in FIG. 10). The angle that isdetermined becomes an error which generates torque that is applied tobring that difference in direction to zero.

The corrective moment is computed as

{right arrow over (τ)}_(corr) =k _(s) {right arrow over (∈)}−k_(d){right arrow over (ω)}

-   -   Where {right arrow over (∈)} is the orientation error, {right        arrow over (ω)} is the measured angular velocity of the handle,        and k_(s) and k_(d) are the stiffness and damping gains,        respectively.

This method allows for the consolidation of UI mechanisms used tocontrol multiple types of devices. Rather than requiring separate UI'sfor different surgical systems (eg 4DOF UI to control a laparoscopicrobot such as that described in WO 2007/088206, WO 2008 049898, and a6DOF (or greater) UI for systems such as a laparoscopic robot usinginstruments that include additional degrees of freedom such asarticulation or wristed motion, or a true Cartesian motion roboticsurgical system, a single 6DOF (or greater) UI may be used with eachtype of system by using haptic actuators to artificially constrain themotion of the UI mechanism such that it feels to the user to be a 4DOFUI when 4DOF is needed.

This method thus allows for a greater-than-4DOF UI to be used to controla 4DOF device (to mimic laparoscopic motion). It also allows forcreation of a virtual RCM which can be placed arbitrarily within theworkspace and can be moved at any point before or during a procedure, ifdesired. For example, the system might have an RCM pre-set at a defaultposition, but include an RCM setting mode in which the user can select adifferent RCM for a particular one of the instruments.

When in the RCM setting mode, the user could, for example, move thecorresponding handle to certain point and space and then give input tothe system that triggers the system to calculate where the handle ispositioned. The input device could be a switch or other form of input onthe UI handle, a keypad, keyboard or other form of input device at theconsole, a sensor for voice activated input, or any other input devicethat could be used to select RCM setting mode.

In an alternative approach, an impedance controller is implemented toforce the motion of the user interface to always pass through the RCM.As with the first approach, this electronically constrains the motion ofthe powered user interface device such that the motion of the userinterface handle will mimic laparoscopic motion.

Referring again to FIG. 10, using this alternative method an RCMconstraint algorithm determines the torques that need be applied to theactuators of the user interface to force the y-axis of the control axes(a set of coordinate axes that are located on the user interface andwhose orientation is known based on the kinematics of the user interfacemechanism) to intersect the virtual RCM. Steps of the RCM constraintalgorithm including the following:

-   -   (1) Computing the vector from the control point P (a point        located on the user interface, such as on the handle, the        position of which is known based on the kinematics of the user        interface mechanism) to the RCM (line 2 in FIG. 10), and find        the projection of that vector onto the y-axis of the control        axes (line 3 in FIG. 10) The point at which the projection        intersects the y-axis (line 1) of the control axes will become a        second control point, point B.    -   (2) Finding the vector connecting the RCM and point B calculated        in step 1 (line 4 in FIG. 10). This vector represents the point        of closest approach of the control y-axis and the RCM.    -   (3) Implementing an impedance controller that will apply a force        to the user interface (via the user interface actuators) that is        in the direction of, and having a magnitude that is proportional        to, the vector obtained in step 2. The impedance controller can        also include damping that is proportional to the rate of the        change of the vector obtained in step 2, as well as inertial        terms to compensate for the accelerating mass of the user        interface.

The below equations describe this above controller (excluding theinertial terms):

F _(actuators) =J _(B) ^(T)(Kr _(RCM/B) +b{dot over (r)} _(RCM/B))

Where J_(B) ^(T) is the transpose of the displacement Jacobian ofcontrol point B, K is a 6×6 diagonal stiffness matrix, b is a 6×6diagonal damping matrix, and r_(RCM/B) is a vector from the RCM to pointB (line 4 of FIG. 10B).

While the above methods are described in the context of enabling asingle user interface configuration to be used to control a surgicalrobotic system in more than one way, e.g. laparoscopic or true Cartesianmotion, these methods are also useful for creating arbitrary constraintsin the user interface work space. For example, they can be used to forcethe user interface to re-trace motions that have been previouslyexecuted for pre-programmed. This can be useful in surgeon training,among other things.

The above method may be further enhanced by attaching the virtual RCM tothe user interface mechanism in the sense that it will move with theuser interface mechanism. In this way the user will experience thepresence of a fulcrum (thus feeling familiar to a laparoscopic surgeon)but will be permitted to relocate the fulcrum to achieve more dexterousmotion and greater range of motion of the surgical instrument beingcontrolled.

In accordance with this enhanced method, the moveable RCM constraintalgorithm determines the torques that need be applied to the actuatorsin the user interface to force the y-axis of the control axes (a set ofcoordinate axes that are located on the user interface and whoseorientation is known based on the kinematics of the user interfacemechanism) to intersect the virtual RCM in the manner described above.Additionally, the location of the virtual RCM is constantly updated byan RCM update algorithm that will move the RCM in the direction ofinsertion of the user interface. In that regard the motion is similar tothat of a wheelbarrow—it only moves in the direction that it ispointing, and the can pivot about the “wheel” to commence movement in adifferent direction. Once movement has begun, the pivot point/RCM (frontwheel) moves with the handle.

An example of the RCM update algorithm is as follows:

-   -   (1) Compute the vector from the control point P (a point located        on the user interface that whose position is known based on the        kinematics of the user interface mechanism) to the RCM (line 2        in FIG. 10B), and find the projection of that vector onto the        y-axis of the control axes (line 3 terminating at point B in        FIG. 10B).    -   (2) Advance the RCM in the direction of the y-axis of the        control axes by adding the projection vector computed in        step (1) to the current location of the RCM.

Meanwhile, as described above, an impedance controller will apply aforce to the user interface (via the user interface actuators) that willtend to bring the y-axis of the control axes to intersect the RCM. Thiswill have the effect of providing a laparoscopic feel to the user. Theaddition of the moveable RCM will then allow the user to “steer” the RCMand ultimately locate the instrument in more favorable positions forperforming surgical tasks.

All prior patents and patent application referenced herein, includingfor purposes of priority, are incorporated herein by reference.

1. A powered user interface for a robotic surgical system having amanipulator and a surgical instrument mounted to the manipulator, thepowered user interface including: a base; a handle on a linkageconfigured to permit movement of the handle in at least six degrees offreedom with respect to the base; actuators operatively associated withjoints of the linkage; a computing device programmed to selectivelyoperate the actuators in accordance with: a first mode of operation inwhich a plurality of the actuators are operated to constrainpredetermined ones of the joints to permit motion of the handle in only4DOF with respect to the base, and a second mode of operation in whichthe actuators permit motion of the handle in at least 6DOF with respectto the base.
 2. The user interface of claim 1, wherein in the first modeof operation the motion is constrained to the DOFs of pitch, yaw, rolland insertion.
 3. The user interface of claim 2, wherein the pitch andyaw motion is constrained with respect to a virtual fulcrum in a workspace of the user interface, and wherein insertion motion is constrainedalong an axis passing through the virtual fulcrum.
 4. The user interfaceof claim 2, wherein the first mode of operation simulates laparoscopicmotion of the handle with respect to a virtual fulcrum in a work spaceof the user interface.
 5. The user interface of claim 4, wherein thehandle includes an insertion axis and wherein, in the first mode ofoperation, the actuators generate corrective moments to maintain theorientation of the insertion axis such that is passes through thevirtual fulcrum.
 6. The user interface of claim 4, wherein the handleincludes an insertion axis and wherein, in the first mode of operation,the system implements an impedance controller to cause the insertionaxis to remain oriented passing through the virtual fulcrum.
 7. The userinterface of claim 1, wherein the computing device is further programmedto determine, based on measurements obtained using sensors at themanipulator, an estimate of forces exerted onto the instrument, and tooperate the actuators to deliver at the handle haptic feedbackcorresponding to the estimated forces.
 8. The user interface of claim 3,wherein the computing device is further programmed to perform a virtualfulcrum setting mode in which a user is prompted to give input to thesystem selecting a desired point in space for the virtual fulcrum, andin which the computing device sets the selected point in space as thevirtual fulcrum.
 9. The user interface of claim 8, wherein the computingdevice is programmed to operate in the virtual fulcrum setting mode at atime when movement of the manipulator is not being actively controlledusing input from the user input device.
 10. The user interface of claim8, wherein the computing device is programmed to operate in the virtualfulcrum setting mode at a time when movement of the manipulator is beingactively controlled using input from the user input device, with thevirtual fulcrum optionally being constantly updated during activecontrol of the manipulator using input from the user input device. 11.The user interface of claim 1, wherein the system further includes amemory in which user interface motion constraints are stored, and inwhich the computing device is programmed to operate in a mode ofoperation in which the plurality of actuators are operated in accordancewith the programmed interface motion constraints to constrain usermovement of the handle to follow a predetermined pattern.
 12. The userinterface of claim 11, wherein the computing device is furtherprogrammed to prompt a user to move the user interface in accordancewith a movement pattern to be stored in memory, to operate in arecording mode in which it determines and records position andorientation data corresponding to the position and orientation of aportion of the user interface as the user moves the user interface inthe movement pattern, and wherein in the mode of operation the pluralityof actuators are operated to constrain user movement of the handle inaccordance with the recorded movement pattern. 13-23. (canceled)
 24. Amethod of using a powered user interface to control a robotic surgicalsystem having a manipulator and a surgical instrument mounted to themanipulator, including: generating input signals in response to movementof a handle of a user interface; causing movement of the manipulator orsurgical instrument in accordance with the input signals; selectivelyoperating actuators of the user interface in accordance with: a firstmode of operation in which a plurality of the actuators are operated toconstrain predetermined ones of the joints to permit motion of thehandle in only 4DOF with respect to the base, and a second mode ofoperation in which the actuators permit motion of the handle in at least6DOF with respect to the base.
 25. The method of claim 24, wherein inthe first mode of operation the motion is constrained to the DOFs ofpitch, yaw, roll and insertion.
 26. The method of claim 25, wherein thepitch and yaw motion is constrained with respect to a virtual fulcrum ina work space of the user interface, and wherein insertion motion isconstrained along an axis passing through the virtual fulcrum.
 27. Themethod of claim 25, wherein the first mode of operation simulateslaparoscopic motion of the handle with respect to a virtual fulcrum in awork space of the user interface.
 28. The method of claim 27, whereinthe handle includes an insertion axis and wherein, in the first mode ofoperation, the actuators generate corrective moments to maintain theorientation of the insertion axis such that is passes through thevirtual fulcrum.
 29. The method of claim 27, wherein the handle includesan insertion axis and wherein, in the first mode of operation, thesystem implements an impedance controller to cause the insertion axis toremain oriented passing through the virtual fulcrum.
 30. The method ofclaim 24, further including determining, based on measurements obtainedusing sensors at the manipulator, an estimate of forces exerted onto theinstrument, and operating the actuators to deliver at the handle hapticfeedback corresponding to the estimated forces.
 31. The method of claim26, further including performing a virtual fulcrum setting mode in whicha user is prompted to give input to the system selecting a desired pointin space for the virtual fulcrum, and in which the computing device setsthe selected point in space as the virtual fulcrum.
 32. The method ofclaim 31, wherein the virtual fulcrum setting mode is performed at atime when movement of the manipulator is not being actively controlledusing input from the user input device.
 33. The method of claim 31,wherein the virtual fulcrum setting mode is performed at a time whenmovement of the manipulator is being actively controlled using inputfrom the user input device, with the virtual fulcrum optionally beingconstantly updated during active control of the manipulator using inputfrom the user input device.